This project aims to map the distribution of chemically specified Purkinje cells in the rat's cerebellar cortex and to correlate their pattern with the parasagittal zones of identified afferents to the cerebellar cortex. Immunocytochemical methods will be used to identify and trace the afferent systems. Electron microscopy will be used to correlate the microzones of chemically specific Purkinje cells with afferents of particular origins. These studies open a new field of neuroanatomy in which the cellular architecture of the brain is analyzed in terms of the connections list made by chemically specified neurons. The cerebellar circuits can serve as a model for other parts of the mammalian brain. Since the cerebellulm is an important integrating center for the control of movement, the hereditary cerebellar degenerations, Parkinson's disease, and the cerebellar degenerations associated with chronic alcoholism, thiamine deficiency, and carbon monoxide poisoning.